Sun visors in motor vehicles frequently include mirror assemblies, some of which provide illumination to facilitate use of the mirror in low light conditions. Typically, prior art visors have supplied this illumination through a light source attached to the visor and designed to emit light at either constant or variable intensity. In the latter case, the intensity of the light source is controlled by an electrical rheostat or potentiometer which varies the voltage applied to the light source. The intensity of the light emitted from the light source is proportional to the voltage applied to the light source. For example, as the rheostat or potentiometer increases the voltage applied to the light source, the intensity of the light source increases.
One shortcoming of known variable intensity lighted visors is that the light emitted at low intensity settings is yellowish in color, a condition which many users find less desirable than white light. Another shortcoming is that control of the light intensity through electrical means, such as a rheostat or potentiometer, increases the cost of the visor. Still another shortcoming is that control of the light intensity by way of electrical means is not entirely reliable.